To take the first point first: the word “pepper” does not make people sneeze, though according to the law it should.[4] Words which describe succulent foods will make the mouth water; voluptuous words will have some of the effect that would be produced by the situations they suggest; but no words will produce sneezes or the reactions appropriate to tickling. In the diagram given by Dr. Watson (p. 106), there are four reflexes which appear to be not sources of conditioned reflexes, namely sneezing, hiccoughing, blinking, and the Babinski reflex; of these, however, blinking, it is suggested (p. 99) may be really itself a conditioned reflex. There may be some quite straightforward explanation of the fact that some reactions can be produced by substitute stimuli while others cannot, but none is offered. Therefore the law of the conditioned reflex, as formulated, is too wide, and it is not clear what is the principle according to which its scope should be restricted. [4] Dr. Watson apparently entertains hopes of teaching babies to sneeze when they see the pepper box, but he has not yet done so. See _Behaviorism_, p. 90. The second objection to Dr. Watson’s law of habit, if valid, is more important than the first; but its validity is more open to question. It is contended that the acts by which solutions of problems are obtained are, in cases of a certain kind, not random acts leading to success by mere chance, but acts proceeding from “insight”, involving a “mental” solution of the problem as a preliminary to the physical solution. This is especially the view of those who advocate _Gestaltpsychologie_ or the psychology of configuration. We may take, as typical of their attitude on the subject of learning, Köhler’s _Mentality of Apes_. Köhler went to Tenerife with certain chimpanzees in the year 1913; owing to the war he was compelled to remain with them until 1917, so that his opportunities for study were extensive. He complains of the maze and cage problems set by American investigators that they are such as _cannot_ be solved by intelligence. Sir Isaac Newton himself could not have got out of the Hampton Court maze by any method except trial and error. Köhler, on the other hand, set his apes problems which could be solved by what he calls “insight”. He would hang up a banana[5] out of reach, and leave boxes in the neighbourhood so that by standing on the boxes the chimpanzees could reach the fruit. Sometimes they had to pile three or even four boxes on top of each other before they could achieve success. Then he would put the banana outside the bars of the cage, leaving a stick inside, and the ape would get the banana by reaching for it with the stick. On one occasion, one of them, named Sultan, had two bamboo sticks, each too short to reach the banana; after vain efforts followed by a period of silent thought, he fitted the smaller into the hollow of the other, and so manufactured one stick which was long enough.